Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a spinnerette plate for
melt-spinning fiber and to a melt-spinning process for preparing
fiber using such spinnerette plate. More particularly, this
invention relates to a spinnerette plate having a plurality of
counterbores and at least three capillaries per counterbore and
to the use thereof in melt~spinning fiber from a fusion melt of
acrylonitrile polymer and water.
In conventional melt-spinning of fibers, a fiber-
forming polymer is heated to a temperature at which it melts,
is extruded through a spinnerette plate to form filaments which
rapidly cool to become solid, and the resulting filaments are
then further processed to provide the desired fiber. The spin-
nerette plate that is employed in such processing must contain
capillaries to provide the desired filaments while satisfying
two additional requirements. The capillaries must be of such
dimensions as to satisfy back-pressure requirements and must be
sufficiently spaced from one another as to prevent premature
contact between the emerging filaments that would result in
sticking together or fusion of filaments with one another. To
reduce back-pressure, the capillaries are provided with counter-
bores of sufficient diameter and depth.
Recent developments in the field of fiber spinning,
especially acrylic fibers, have led to the development of fusion
melts which can be extruded through a spinnerette plate to pro-
vide filaments. These fusion melts comprise a homogeneous com-
position of a fiber-forming acrylonitrile polymer and water~
Water enables the polymer to form a melt at a temperature below
which the polymer would normally melt or decompose and becomes
intimately associated with the molten polymer so that a single-
phase melt results. Water must be used in proper proportions
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with the polymer to provide the single-phase fusion melt.
Since the temperature at which the fusion melt forms is above
the boiling point of water at atmospheric pressure, super-atmos-
pheric pressures are necessary to keep water in the system.
Such fusion melts have been effectively spun into fiber using
spinnerette plates similar to those employed in conventional
melt-spinning.
Because of the requirement for adequate spacing of
the capillaries in spinnerette plates used for conventional
melt-spinning to prevent premature contact between the nascent
filaments which would result in their sticking together, the
number of capillaries that can be provided in a given spinner-
ette plate is greatly restricted. As a result, production
capacity of a spinnerette with a given surface area is limited
and usually large tow bundles can only be produced by combining
the outputs from a series of spinnerettes. This, in turn, re-
quires costly installations of additional spinnerettes, special-
ly designed conduits and spin packs to ensure an ev~n distribu-
tion of the melt to all spinning holes, provision of space for
installation, and further power consumption to operate the in-
creased number of spinnerettes.
There exists, therefore, the need for a single spin-
nerette plate that would overcome the problems associated with
prior art spinnerette plate assemblies and enable increased
production to be obtained. There also exists the need for pro-
cesses for providing fiber by melt spinning which enables the
productivity of spinnerette plates to be increased. Such pro-
visions would fulfill long-felt needs and constitute significant
advances in the art.
In accordance with the present invention, there is
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provided a spinnerette plate for melt-spinning fiber having a
plurality of counterbores and within each counterbore, at least
about 3 capillaries, said capillaries being at a density of at
least about 18 per square centimeter of plate surface.
In:accordance with the present invention, there is
also provided a process for melt-spinning an acrylonitrile poly-
mer fiber which comprises providing a homogeneous fusion melt
of a fiber-forming acrylonitrile polymer and water at a tem-
perature above the boiling point of water at atmospheric pres-
sure and at a temperature and pressure which maintains water and
said polymer in a single phase and extruding said fusion melt
through a spinnerette assembly containing a spinnerette plate
having a plurality of counterbores and within each counterbore
at least about 3 capillaries, said capillaries having a density
lS of at least about 18 per square centimeter of plate surface
and extruding said fusion melt directly into a steam-pressurized
solidification zone maintained under conditions such that the
rate of release of water from the nascent extrudate avoids de-
formation thereof.
~he present invention by employing a fu~ion melt of
fiber-forming acrylonitrile polymer and water at a temperature
above the boiling point of water at atmospheric pressure and at
a temperature and pressure that maintains water and the polymer
in a single phase and by spinning said fusion melt directly
into a steam-pres~uri~ed solidification zone that controls the
rate of release of water from the nascent extrudate 50 that de-
formation thereof is avoided, filamentary extrudates are pro-
vided which do not stick together or become deformed as they
emerge from the spinnerette capillaries. Since in this pro-
cess the filaments have no tendency to stick together or deform
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as the emerge from the spinnerette, the counterbores of the
spinnerette plate can be located closer together and more than
one capillary can be provided in the counterbores. As a result,
the productivity of the spinnerette can be greatly increased
without negatively affecting the quality of the resulting fiber.
The spinnerette plate of the present invention, con-
tains a number of capillaries located within each counterbore.
The counterbores are necessary to enable the spinnerette plate
to operate at a suitable level of back-pressure. The spinner-
ette plate as a whole will contain a substantially greater num-
ber of capillaries than the prior art spinnerette plates assoc-
iated with melt spinning because the problem of sticking to-
gether of nascent extrudates is eliminated. Increased pro-
ductivity is provided by increasing the density of capillaries
in the spinnerette plate and the number of capillaries in each
counterbore beyond the operative limits of conventional melt-
spinning spinnerette plates which have restrictions as to hole
density imposed by fusing of individual filaments.
It is possible to provide larger counterbores than
are normally associated with a capillary and provide numerous
capillaries therein although this has often been found to be
unnecessary. It is preferable to provide a pattern of counter-
bores more closely spaced than those in the prior art spinner-
ette plates for melt spinning in a pattern providing uniform
extrusion of the spinning melt through the spinnerette plate.
The combination of more closely spaced counterbores with a
plurality of capillaries within each counterbore gives rise to
a substantial increase in the total number of capillaries for a
given spinnerette surface, and hence in the productivity of the
spinnerette.
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A typical spinnerette plate of the present invention
is shown in the accompanying drawings, in which Figure 1 repre-
sents a top view of the spinnerette plate showing the pattern
of counterbores and capillaries therein and Figure 2 shows a
cross-sectional view of the same spinnerette plate showing de-
tails of the counterbores and capillaries.
In carrying out the process of the present invention,
it is necessary to provide a homogeneous fusion melt of a fiber-
forming acrylonitrile polymer and water. Any fiber-forming
acrylonitrile polymer that can form a fusion melt with water at
a temperature above the boiling point of water at atmospheric
pressure and at a pressure and temperature sufficient to main-
tain water and the polymer in a single fluid phase, can be used
in the process of the present invention. Polymers falling into
this category are known in the art. The fusion melt is prepared
at a temperature above the boiling point at atmospheric pres-
sure of water and eventually reaches a temperature and pressure
sufficient to maintain water and the polymer in a single, fluid
phase.
The homogeneous fusion melt thus provided is extruded
through the spinnerette plate of the present invention directly
into a steam-pressurized solidification zone that controls the
rate of release of water from the nascent filaments so that
deformation thereof is avoided and the process is able to pro-
vide filaments which solidify without sticking together one with
another in spite of the close proximity of adjacent capillaries.
The extruded filaments are processed according to conventional
procedures to provide desirable filamentary materials which may
have application in textile and other applications.
The pressurized solidification zone used in the pro-
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cess of the present invention is a critical feature of the pro-
cess. If this pressurized solidification zone is omitted, water
is so rapidly released from the nascent filaments which would
emerge into atmospheric conditions that the filaments would
become inflated or deformed and interfere with neighboring fil-
aments and necessitate reduction in the number of operative
spinnerette capillaries which would defeat the object of the
invention. On the other hand, by employing the presqurized
solidification zone operating at suitable steam pressure, the
rate of release of water can be controlled as the nascent fil-
aments solidify so that foaming and deformation thereof is
avoided and optimum stretching is possible. The particular
pressure of steam will vary widely depending upon the polymer
employed, the spinning temperature employed and the like. The
useful values for given systems a~e those values which minimize
or avoid foaming or other forms of de~ormation of the filaments
and provide optimum stretching. These values can readiIy be
determined for any given system of polymer and water taking into
account the teachings herein given.
A particularly preferred embodiment of the process
of the present invention is drawing the nascent extrudate while
it remains in the steam-pressurized solidification zone. Such
drawing can be accomplished in one or more stretches and can
eliminate any subsequent drawing normally required for fiber
orientation. It is particularly preferred to conduct drawing
in two stages with the stretch ratio of the second stage being
larger than that of the first stage. It is also preferred to
relax the drawn fiber in steam generally under conditions which
provide from about 20% to 35% filament shrinkage.
The invention is more fully illustrated in the exam-
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ples which fo]]ow, wherein all parts and percentages are by
weight unless otherwise specified.
Kinematic molecular weight (Mk) is obtalned ~from ~ ~~
the following relationship: ~ = 1 Mk wherein ~ is the average
effluent time (t) in seconds for a solution of 1 gram of the
polymer in 100 milliliters of 53 weight percent aqueous sodium
thiocyanate solvent at 40C. multiplied by the viscometer factor
and A is the solution factor derived from a polymer of known
molecular weight and in the present case is equal to 3,500.
-~~-~ ~ BXAMPLE 1 ~ ~-~~~~----------- -- ------ _
A fusion melt of 15~ water and 85% of an acrylonitrile
polymer of the following composition was prepared at autogene-
ous pressure and 170C.:
Acrylonitrile 89.3%
Methyl methacrylate 10~7%
Molecular weight, kinematic 58,000
The fusion melt was spun at 170C. through a spinnerette assem-
bly having orifice characteristics as follows:
Capillary diameter 200 microns
Capillary spacingl 0.47 millimeters
Capillaries per counterbore 7
Counterbore diameter1.2 millimeters
Counterbore spacingl4.1 millimeters
Capillary density 62 per sq. cm.
1 center to center
The extrusion was directly into a solidification zone pressuriz-
ed with saturated steam at 15 pounds per square inch. The ex-
truded filament~ were stretched in a first stage at a stretch
ratio of 3.8 and in a second stage at 6~7 for a total stretch
of 25.5 x. The filaments were dried at 138C. and relaxed in
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steam at~ll6C. Fiber of about 12 denier per fiIament was ob- ~~~-~~-
tained having the following properties:
Straight tenacity grams/denier 3.4
Straight elongation % 35
Loop tenacity grams/denier 2.1
Loop elongation % 13
No sticking together of the filaments occurred and
continuous processing was accomplished. --
COMPARATIVE EXAMPLE A
Using the spinnerette assembly described in Example
r~ 1, a melt of polypropylene (Rexene Grade PP 3153) of fiber grade
having a melt index of 3 dg/min. was prepared at 260C. and
extruded into static air at 25C. The melt emerging from the
spinnerette orifices merged to form macrofilaments from the
union of the individual filaments issuing from single capillar-
ies. Thus, filaments of the desired denier were not obtained
using this spinnerette plate design.
EXAMPLE 2
The procedure of Example 1 was again followed with
the following exceptions: The polymer had a kinematic molecular
weight value of 40,000 and the spinnerette assembly had the
following characteristics:
Capillary diameter85 microns
Capillary spacing 0.40 millimeter
Capillary per counterbore 19
Counterbore diameter 2.0 millimeters
Counterbore spacing 1.4 millimeters
Capillary density875 per sq. cm.
Continuous spinning was conducted with no sticking
together or fusion of the individual filaments and fiber of
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113~31~
substantially the same properties as obtained in Example 1
was obtained.
When the polypropylene melt described in Comparative
Example A was extruded, extensive fusion of the individual
filaments occurred and it was not possible to provide the de-
sired filament denier.
,
EXAMPLES 3 ~ 5
Following the procedure of Example 1, a number of
runs were made using spinnerette assemblies of different design
in each run as shown in the table which also gives the example
number. In each instance, continuous spinning was effected
with no sticking together of the individual filaments.
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